Four men have been charged by the Financial Services Authority with taking part in a £3m insider dealing conspiracy in the largest and most complex inquiry into insider trading ever conducted by the regulator.

Those charged with involvement in the conspiracy, between November 2006 and March 2010, include Martyn Dodgson, for much of that time working in senior roles at Deutsche Bank; Ben Anderson, a private stock broker; Iraj Parvizi, an Iranian-born businessman and investor in small-cap stocks; and accountant Andrew Hind.

The four are alleged to have made a profit of £3m from their trading, according to the FSA, which has been conducting investigations for more than two years under the codename of Operation Tabernula. It hinted that there may be more charges to come, saying a number of individuals remain under investigation.

Parvizi's solicitor Peter Hughmans said his client "emphatically denies the charges and is determined to clear his name". Lawyers for Dodgson, who had been promoted to managing director at Deutsche Bank before it became known he was the subject of a criminal investigation, declined to comment. Legal representatives for the other two could not be reached.

Dodgson, who had been part of a Deutsche Bank team advising the government on its stakes in Royal Bank of Scotland and Lloyds Banking Group, was immediately suspended after the FSA raided his workplace in March 2010. He no longer works for the bank. In a statement Deutsche Bank stressed the FSA investigation "concerned one individual [at the bank], Martyn Dodgson, and not the bank itself".

Hind has been a director of a number of companies, one of them called Stock Options Ltd, where he was also a shareholder. His current directorships include Whitdale Ltd, Jacob & Co UK and Deskspace Offices.

The wider Operation Tabernula investigation, carried out jointly with the Serious Organised Crime Agency, had been examining a suspected insider trading ring said to have traded up to £22m. Initial evidence led to raids in March 2010 on the homes and offices of people working for Deutsche Bank, Novum Securities, Exane BNP Paribas and hedge fund Moore Capital. Companies whose share trading has been under scrutiny include Scottish & Newcastle, National Express, Wolseley, Collins Stewart, Barclays and Paragon.

The City regulator has pursued a string of insider dealing cases since admitting in 2008 that its light touch approach to policing the Square Mile was failing. But Operation Tabernula is by far the most significant case – both in terms of the people allegedly involved, the hedge funds and banks they worked for and the sums allegedly traded.

The four men charged were among nine individuals who have been arrested and questioned as part of Operation Tabernula since the co-ordinated dawn raids on 16 addresses across London and the south-east two years ago. At the time of the searches seven men were arrested, including the four charged on Monday.

Since then a further two individuals have been arrested and questioned as part of the inquiry.